1. Technical Field
The present invention relates to a semiconductor laser device having a stem which is formed by pressing a thin sheet metal, and in particular to a semiconductor laser device having an enhanced heat dissipation.
2. Description of Related Prior Art
A stem of the prior art semiconductor laser device, for example as shown in FIG. 10, comprises a base 1, outer leads 4 which are fixed to the base 1 and a heat sink 3 which is a mounting of a silicon sub-mount on which a semiconductor laser light emitting element and the like are mounted. The base 1 is generally formed by forging a disc of an iron having a thickness of 1.2 mm and a diameter of 5.6 mm in a press die. At this time, the heat sink 3 is formed by either pressing and swaging the peripheral edge of the disc or raising the central portion of the disc. The outer leads 4 are fixed to the base by means of an electrically insulating fusing glass 12.
However, since the prior art for manufacturing the stem has such problems as following, it is difficult to decrease the manufacturing cost.
(1) The forging dies use thick metal sheets, resulting in a high cost of material and are liable to wear and to be broken.
(2) Since, a high precision is required for the size of the lateral sides of the base of the stem, forging of the peripheral edge of the disc as well as working of the lateral sides thereof is necessary in case in which manufacturing is achieved by forging.
(3) Bonding between the base and outer lead is conducted by using a low melting point glass having a melting point of about 1000xc2x0 C. Since this melting point is higher than that of gold, plating of the outer lead with gold should be conducted after the leads have been bonded to the base. Accordingly, gold plating should be conducted to meet the requirements of the outer leads although it inherently suffices to plate the base with Ni and the like in the prior art.
The base may be reduced in size for reducing the mounting area if the heat dissipation does not matter so much on mounting on an optical pickup.
Reduction in mounting area for the base which has been formed by a conventional forging method can not be conducted without any cutting work. A simple method such as stamping a blank can not be adopted.
In order to solve such a problem, it may be devised that the base of the stem be formed from a thin sheet metal having a thickness of about 0.1 mm to 0.5 mm by a pressing technique. Unlike the prior art in which the base of the stem is stamped from the relatively thick sheet metal of about 1.2 mm by forging, use of a thin sheet metal provides problems such as low, mechanical strength, bending and warping, as well as a problem that the heat dissipation characteristics is not sufficient in some cases.
With recent development of the light emitting diodes which emit short wave length light and high power light emitting elements, stems having a high heat dissipation ability have been demanded.
The present invention was made in order to solve the above-mentioned problems.
(1) The present invention provides a semiconductor laser device including a stem having a base, a mounting for an laser light emitting element and the like, which is integrally formed on the base, and outer leads, wherein said base is formed by bending a sheet metal so that it has an annular wall.
(2) In a semiconductor laser device of the present invention, said annular wall is formed by bending a sheet metal so that it is spaced from the peripheral edge thereof and the mounting for said laser light emitting element and the like is formed on said annular wall by erecting the upper face of the sheet metal.
(3) In a semiconductor laser device of the present invention, said annular wall is formed by bending a sheet metal so that it is spaced from the peripheral edge thereof and in that the mounting for said laser light emitting element and the like is formed on said annular wall by erecting the upper face of the sheet metal.
(4) In a semiconductor laser device of the present invention, said outer leads are bonded to said base with a thermosetting resin which is charged within said annular wall.
(5) In a semiconductor laser device of the present invention, said outer leads and said base are plated with different materials.
(6) In a semiconductor laser device of the present invention, said annular wall is a heat dissipating fin.
(7) In a semiconductor laser device of the present invention, said stem comprises a base having at its peripheral edge an annular wall which is formed by bending a sheet metal and a heat sink member is sealed in said annular wall.
(8) In semiconductor laser device of the present invention, said heat sink is an insulated copper material.
(9) In a semiconductor laser device of the present invention, said stem comprises a base having at its peripheral edge an annular wall which is formed by bending a cladding material in which two metals having different heat conductivities are cladded to each other in a stripe manner and in that a mounting for the laser light emitting element, which is integrally formed on at least said base is formed of a metal having a higher heat conductivity of said different metals.
(10) In a semiconductor laser device of the present invention, said stem comprises a base having at its peripheral edge an annular wall which is formed by bending a cladding material in which two metals having different heat conductivities are cladded to each other in a stripe manner and only a mounting for the laser light emitting element, which is integrally formed on said base is formed of a metal having a higher heat conductivity of said different metals.
(11) In a semiconductor laser device of the present invention, one of the metals having different heat conductivities is iron and the other is copper.
(12) In a semiconductor laser device of the present invention, comprising a stem having a base, a mounting for mounting an laser device and like and outer leads, said base has an annular wall which is formed by bending a sheet metal; said mounting for mounting the laser light emitting element and the like is mounted on said outer leads; and said outer leads are bonded to said base with a thermosetting resin which is sealed in said annular wall.
(13) In a semiconductor laser device of the present invention set-forth in the preceding paragraph, said heat sink member is also sealed in said annular wall.
Corresponding to the feature as defined in each of the foregoing paragraphs, the present invention provides the advantage as follows:
(1) Since a thin sheet metal is subjected to relatively simple pressing operations such as punching and bending, wear and break of a die is hard to occur. Accordingly, the stem can be formed at a low cost. Even if reduction in pickup mounting area is required, the base can be easily cut only by punching it in a press machine. Since the annular wall is formed by bending a sheet metal, the outer leads can be sealed in an inner space with a thermosetting resin. The strength can be assured although the sheet metal is thin.
(2) Since the thermosetting resin for fixing terminals is curable at low temperatures, the gold-plated terminals can be fixed to the stem. Accordingly, the terminals and the base of the stem can be plated with different materials.
(3) The annular wall can be used as heat dissipating fin and a suitable heat dissipating area can be obtained by adjusting its length.
(4) Heat dissipating ability can be assured by the annular wall formed on the peripheral edge of the base and the heat sink member. The heat dissipating characteristics of the annular wall and the heat sink member can be optimized depending upon the applied semiconductor laser device by adjusting the width of the annular wall and the thickness of the heat sink member.
(5) Since use of materials which are excellent in heat conducting characteristics for unnecessary portion can be considerably restricted, a semiconductor laser device which is excellent in heat dissipation can be obtained at a reduced cost.
(6) Since a material which is excellent in heat conductivity may be combined with a material which is excellent in strength in such a manner that respective characteristics can be advantageously used, a semiconductor laser device having excellent strength and heat dissipating characteristics can be obtained at a reduced cost.
(7) Use of a cladding material comprising a copper and iron materials provides a low cost stem having both high strength and heat dissipation. Accordingly, a semiconductor laser device having an excellent performance can be obtained at a low cost.